Commutator.



No. 662,465; Patented Nov. 27, I900. E. D. PRIEST & G. L. SCHERMERHORN.

COMMUTATOR.

(Application filed June 30, 1900.)

(No Model.)

\Lne $585 Jnventors Edward D. Pm est/,- v George bsohermerhorn UNITEDSTATES PATENT EDWVARD D. PRIEST AND GEORGE L. SCHERMERHORN, OFSCHENECTADY, NEXV YORK, ASSIGNORS TO THE GENERAL ELECTRIC COMPANY, OFNEW YORK.

C O M M U TAT O R.

SPECIFICATION forming part of Letters Patent No. 662,465, dated November27, 1900.

Application filed June 30, 1900. Serial No. 22,128. \No model.)

To all whom it may concern.-

Be it known that we, EDWARD D. PRIEST and GEORGE L. SOHERMERHORN,citizens of the United States, residing at Schenectady, county ofSchenectady, State of New York, have invented certain new and usefulImprovements in Com mutators, (Case No. 1,571,) of which the followingis a specification.

Our present invention relates to commutators for dynamo-electricmachines,and comprises certain improvements by which the wear of suchdevices is minimized and sparking is greatly reduced;

Commutators for dynamo-electric machines are constructed of bars ofcopper arranged usually in a cylindrical structure, and it is necessarythat each bar should be insulated from the adjacent bars of thecommutator. It is common in the construction of comm utators to producethis insulation by the insertion of strips of mica, each strip cut to ashape similar to that of the commutator-seg ments. The commutator isbuilt up by alternating mica strips with copper bars. Such a commutatorin a form now largely used in commercial Work is shown in the patent toWilliam B. Potter, No. 608,299, August 2, 1898. We have found that incommutators of this and other usual types great difficulty has beenexperienced by reason of the hardness of the mica, which is the onlyinsulating material commonly used. Such commutators are usually run inconnection with carbon brushes, and in practical operation the cop persegments wear down faster than the mica strips, owing to the fact thatmica is an exceedingly hard and tenacious material and is notdissipated, asis the copper, by the minute arcs which exist on even thebest commutators. The result is that after a certain time some or all ofthe mica strips project slightly, perhaps only one-half tothree-hundredths of an inch, above the general surface of thecommutator. It will be obvious that when this occurs the brushes willtend to jump more or less each time they strike one of these projectingmica strips, and each time that this jumping oc curs there mustnecessarily exist a powerful are. For example, in a railway-motor eachbrush will frequently carry during acceleration more than one hundredamperes at live hundred volts-,and the very slightestinterruption of thecontinuity of a circuit carrying such current is sure to result indestructive arcing. We have found in actual commercial work thatnumerous unexplained difliculties with the commutation of railwayanotorsand other pieces of apparatus have been directly traceable to thiscause.

Our present invention aims at preventing or reducing this action; and itconsists in cutting down the mica strips so that they do not tend toreach or rise above the general surface of the commutator. This may beac complished with an existing commutator by simply grooving down eachmica strip with a suitable steel tool or saw until the strip in questionis brought from one thirty-second to three thirty-seconds of an inchbelow the surface of the commutator. In applying our invention tocommutators in the course of OOI1 struction in the factory we may buildthe mica strips from one thirty-second to three thirty-seconds of aninch narrower than the copper segments and assemble the com mutator insuch manner as to leave each mica strip the proper distance below thesurface, or we may build the commutator as usual and cut down the mica,as above explained. We have been able by this simple expedient to causethe perfectly satisfactory operation of various motors and generatorswhich have heretofore been accustomed to spark very seriously, and wehave been able to reduce the wear and add to the life of commutators onsuch machines and on many other machines.

Referring to the drawings attached hereto, which show a manner in whichour invention may be applied, Figure 1 is an elevation, partly insection, of a commutator; and Fig. 2 is a cross-section on the line 2 2of Fig. 1.

The drawings represent our invention as applied to a commutator of thetype shown in the above-mentioned patent to William B. Potter, though itwill be clear that our invention may be applied to any known type ofcommutator in which copper bars alternate with strips of hard insulatingmaterial.

The commutator-segments A are mounted on a cast-metal shell B, whichshell is provided at one end with conical flange C, formed integraltherewith, and at the other end with an adjustable clamping-ring D. Theclam ping-ring and flange are each provided with conical surfaces whichengage corresponding surfaces on the segments and hold the latter inplace. Between the conical surface of the clamp and the correspondingsurfaces of the segments are layers of insulating material E, whichinsulate the segments from the supportingshell. The clamping-ring D isheld in place and adjusted by the nut G, and is prevented from turningby the pin H, which enters a slot 1 formed therein. The nut G isprevented from loosening by means of one or more screws J. The underside of each bar is provided with a lug K, having angular 0r conicalclamping-faces K, with which the conical flange C and the adjustingringD engage. The portion M of each magnet is slotted at M to receive thearmature leads N, and between the portions M and the wearing-surface isa circumferential slot or groove L, into which the leads N extend.

Thus far we have described the Pottercommutator as it is used inpractice. In accordance with our present invention the mica strip F iscut down slightly below the general surface of the commutator,as isclearly shown in Figs. 1 and 2,whereby the beneficial results abovedescribed are obtained. It has been suggested that com in u tators thusconstruct ed would be open to the objection that the spaces F, existingover the insulating-strips, would tend to fill with carbon-dust andcopper-dust and cause a short circuit. We find in practice that thisobjection does not exist, provided the strips are only cut down a fewthirty-seconds of an inch, the exact amount depending, of course, uponthe size of the par ticular commutator, the thickness of the mica, andother factors.

Though we prefer, above described, to cut out the whole width of themica, it is, nevertheless, possible to secure the benefits of ourinvention in whole orin part by weal:- ening the mica for the distanceindicated, or, for example, by grooving out the center of the mica,leavinga strip of, say, five millimeters thickness, extending to thelevel of the commutator-surface on each side, as indicated roughly at O.

The essential feature is that the mica should be so cut down as toprevent it from extending above the commutator after the segments haveworn. and producing the harmful action above described. This and othersuch modifications we aim to include in our claims.

"What We claim as new, and desire to secure by Letters Patent of theUnited States, is

1. A commutator composed of segments of conducting material separated byinsulation not extending to the general level of the segments.

2. A commutator for dynamo-electric machines, consisting of alternatestrips of copper and mica, the mica being grooved out for a shortdistance below thelevel of the copper.

3. As an article of manufacture, a commutator composed of alternatestrips of copper and mica adapted to be clamped upon a shell,

the mica strips being narrower than the cop-,

per strips.

4-. A commutator for dyname-electric machines, consisting of alternatestrips of copper and insulation, the insulation being grooved out for ashort distance below the level of the copper.

5. A commutator having the insulation between segments cnt down belowthe surface of the segments.

In witness whereof we have set our hands this 28th day of June, 1900.

EDVARD D. PRIEST. GEORGE L. SOHERMERHORY.

\Vitnesses:

BENJAMIN B. HULL, MABEL H. EMEnsoN.

